Effect of nitrogen fertilizer on the resistance of rice near-isogenic lines with BPH resistance genes

Background: Nitrogen is an essential macronutrient for plant growth and development. Crops with a high nitrogen input usually have high yields. However, outbreaks of brown planthoppers (Nilaparvata lugens; BPH) frequently occur on rice farms with excessive nitrogen inputs. Rice plants carrying BPH resistance genes are used for integrated pest management. Thus, the impact of nitrogen on the resistance of rice near-isogenic lines (NILs) with BPH resistance genes was investigated. Results: We tested these NILs using a standard seedbox screening test and a modified bulk seedling test under different nitrogen treatments. The amount of nitrogen applied had an impact on the resistance of some lines with BPH resistance genes. In addition, three NILs (NIL-BPH9, NIL-BPH17, and NIL-BPH32) were further examined for antibiosis and antixenosis under varying nitrogen regimes. The N. lugens nymph population growth rate, honeydew excretion, female fecundity, and nymph survival rate on the three NILs were not affected by different nitrogen treatments except the nymph survival rate on NIL-BPH9 and the nymph population growth rate on NIL-BPH17. Furthermore, in the settlement preference test, the preference of N. lugens nymphs for IR24 over NIL-BPH9 or NIL-BPH17 increased under the high-nitrogen regime, whereas the preference of N. lugens nymphs for IR24 over NIL-BPH32 was not affected by the nitrogen treatments. Conclusions: Our results indicated that the resistance of three tested NILs did not respond to different nitrogen regimes and that NIL-BPH17 exerted the most substantial inhibitory effect on N. lugens growth and development.